Intermolecular interactions of the CX3OCHO dimers, and complexes CX3OCHO–n(H2O), CX3OCHO–n(HO2) (X = H,F; n = 1,2)

Abstract

The intermolecular interaction energies of the CX₃OCHO dimers, CX₃OCHO–n(H₂O), and CX₃OCHO–n(HO₂) (X = H,F; n = 1,2) complexes are studied by using molecular orbital calculations at the (U)MP2/aug(df,pd)-6-311G**//(U)B3LYP/6-311G** level. We first confirmed the reliability of this level of calculation by utilizing examples of two complexes, CH₃OCHO–HO₂ (syn) and CF₃OCHO–HO₂ (syn). The calculated intermolecular interaction energies for the formate dimers (−3.75 to −5.19 kcal mol⁻¹) and CX₃OCHO–H₂O (−2.39 to −4.90 kcal mol⁻¹) are relatively small. On the other hand, the CX₃OCHO–HO₂ complexes have larger interaction energies (−4.78 to −9.69 kcal mol⁻¹). The complexes, CX₃OCHO–2(H₂O) and CX₃OCHO–2(HO₂), have the largest intermolecular interaction energies (−12.42 to −13.89 kcal mol⁻¹ and −14.47 to −18.39 kcal mol⁻¹, respectively). Except for the formate dimer of syn–syn type, the interaction energies for the complexes with CF₃OCHO are always smaller than the corresponding complexes with CH₃OCHO. Finally, we estimated the concentrations of the complexes in the low and high water concentration conditions. In conclusion, it has been observed that the complexes studied in this work are not likely to form in the atmosphere.